Scanner scanner=new Scanner(System.in);
		int score=scanner.nextInt();
		switch (score/10) {
		case 10:
		case 9:
		case 8:System.out.println("A");break;
		case 7:
		case 6:System.out.println("B");break;
		case 5:
		case 4:System.out.println("C");break;
		case 3:
		case 2:
		case 1:
		case 0:System.out.println("D");break;
		default:System.out.println("数据输入错误。");
